A known component associated with AR-15 and M16 style rifles is the action assembly, this most basically including a reciprocating bolt subassembly mounted upon a receiver plate and which is integrated into the upper receiver in communication with a magazine ammunition feed incorporated into an engaged lower receiver. Disassembly and modification of the action assembly is often desired, such as in instances where sub caliber conversion is desired (e.g. such as to modify the action assembly originally constructed for use with center fire cartridges so as to permit firing of lesser expensive rim fire cartridges.
The tension and dimensional tolerance of the receiver frame is also critical to the proper functioning of the firearm and the removal of the bolt and associated chamber adapter often results in undesirable changes being made to critical frame dimensions.